Cell colony with induced pluripotent stem cells stained in red using the TRA method.
The U.S. Patent and Trademark Office issued a patent to two scientists from UCLA’s Eli & Edythe Broad Center of Regenerative Medicine & Stem Cell Research for a method to identify human-induced pluripotent stem cells in the lab. The method developed by William Lowry, PhD, and Kathrin Plath, PhD, uses a tumor rejection antigen (TRA) to identify stem cells derived from adult skin or blood cells that have successfully been coaxed in the lab back into an embryonic-like pluripotent state.
“Using the TRA method is an important validation step to ensure that the target cells have potentially been reprogrammed to a pluripotent state,” says Dr. Plath, professor of biological chemistry. “This accurate identification of reprogrammed cells is critical, as we conduct research to better understand the viability of pluripotent stem cells for therapeutic treatments for human disease.”
Because these so-called induced pluripotent stem cells (iPSCs) are created from a patient’s own cells — as opposed to human embryonic stem cells, which are created from a donated frozen human embryo — there is little risk of rejection if they are used to treat disease in that patient. Nevertheless, some risks have been identified in the reprogramming process. Since iPSCs do not begin their existence in a pluripotent state, scientists must validate that the donor cells indeed have been reprogrammed into iPSCs to ensure the right kinds of cells are used in research. And as stem-cell science moves from the lab to clinical treatments, validating the cells has become a critical step in ensuring that stem-cell treatments are ready for human clinical trials.
“As we work to understand if iPSCs are safe for human trials, it’s vitally important that we’re working with the right cells,” says Dr. Lowry, associate professor of molecular, cell and developmental biology. “That’s where the TRA method comes in.” Prior to the use of the TRA method, the process of picking pluripotent stem cells out of other cellular matter in a petri dish was much like trying to find a needle in a haystack. Scientists reprogrammed adult cells with the intent of achieving pluripotency, but to validate the pluripotent state of the cells, they had to be stained in a way that caused them to die. As a result, scientists had to use a complex duplication system to keep a copy of the stem-cell collection they were testing so they would still have living cells once pluripotency was established.
The TRA method makes that step unnecessary. When added to reprogrammed human cells in a petri dish, TRA recognizes and binds to a molecule that only exists on human pluripotent stem cells. Attaching a color to the antibody stains the pluripotent cells without harming them. This method allows for easy viewing and results in the accurate identification and selection of potential pluripotent cells. The TRA staining method is now the standard first step in most research studies involving iPSCs.